Overload relief structure



Jan. 24, 1939. O MELMER 2,144,769

OVERLOAD RELIEF STRUCTURE Filed March 10, 1938 3 Sheets-Sheet 1 INVENTOR Z'rz 0. ins/men Jan. 24, 1939. E. Q. MELMER 2,144,769

OVERLOAD RELI EF' STRUCTURE Filed March 10, 1938 3 Sheets-Sheet 2INVENTOR .Z'rzc a 77elwer:

like :1 TTOR/VE Y5.

Jan. 24, 1939. 5 5 MELMER 2,144,769

OVERLOAD RELIEF STRUCTURE Filed March 10, 1938 3 Sheets-Sheet 3 11vVENTOR BY 572 4 0. Melzrzer:

A TTORNE Y5:

Patented Jan. 24, 1939 I UNITED STATES PATENT OFFICE OVERLOAD RELIEFSTRUCTURE Application March 10,

7 Claims.

This invention relates to automatic overload control devices; andparticularly relates to such devices which automatically actuate acontrol switch, or the like, for cutting out a machine upon overload tothereby prevent injury to the machine.

One of the primary objects of the present invention is to provide anoverload control mechanism which becomes more sensitive as the loadincreases and which is most sensitive when the load approaches itscontrolled maximum.

Another object of the invention is to provide an overload control deviceinterposed between driving and driven members which is operable foreither direction of rotation of the driving member and which includesresilient connections for both directions of rotation, respectively, soconstructed and arranged that upon rotationjin one direction onlycertain: of the resilient means are loaded and the others idle, and uponrotation in the reverse direction the others are loaded and the firstidle.

A further object of the invention is to provide a lost motion connectionbetween the resilient means, in the type of control device mentioned,and the driving or driven means so that upon rotation in one direction,only certain of the resilient means are loaded while the others are idleand relaxed, thereby lengthening the life of the device.

Another object of the invention is to provide a roller connectionbetween an axially movable annular or ring member and an elongated slotin one of the members of the driving or driven connection so that thering may be moved axially in a relatively free manner without undue wearon the parts, thereby insuring a positive and tight connection betweenthe parts.

' Another object of the invention is to provide an overload controldevice which is adapted for a variety of different uses such as in thedriving connections of multiple or single drive conveyer systems,flexible shaft couplings, and the like.

Other objects of the invention will become apparent from the followingspecification, the drawings relating thereto, and the claims hereinafterset forth.

In the drawings, in which like numerals are used to designate like partsin the several views throughout:

Figure 1 is a vertical cross-sectional view through a control mechanismembodying features of the present invention;

Fig. 2 is a fragmentary, cross-sectional view 1938, Serial No. 195,205

on a slightly reduced scale taken substantially along the line 2-2 ofFig. 1;

Fig. 3 is a fragmentary, cross-sectional view on a slightly reducedscale, taken substantially along the line 3-4 of Fig. 1;

Fig. 4 is a fragmentary, cross-sectional view on a slightly reducedscale taken substantially along the line 4--l of Fig. 1;

Fig. 5 is a diagrammatic developed view of the cam ring illustrated inFigs. 1 and 2;

Fig. 6 is a view similar to Fig. 2 with certain of the parts removeddiagrammatically illustrating the structure in various positions duringoperation;

Fig. '7 is a cross-sectional view with parts in elevation takensubstantially along the line 'l--| of Fig. 1;

Fig. 8 is a view similar to Fig. 1, illustrating the present inventionas applied to a flexible coupling; and

Fig. 9 is a fragmentary, cross-sectional view on a slightly reducedscale taken substantially along the line 99 of Fig. 8.

Referring to the drawings, and referring particularly to Figs. 1 to '7,an overload control device embodying features of the present inventionis illustrated which is particularly adapted for use with eithermultiple or single drive units for conveyer systems. The control deviceillustrated includes a driven shaft I0 adapted for suitable connectionto a conveyer mechanism. The shaft I0 is connected to a driven member l2for rotation therewith by a key M, and has diametrically opposed,radially extending, lever arms I6 and I8. The lever arms 16 and I8 haveaxially extending bosses I1 and I9, respectively, at the outer endsthereof which are adapted to be connected to spring members in a mannerto be 7 described in detail hereinafter. The bosses l1 and I9 may beeither formed integral with the lever arms I6 and I8 or may beformedseparately and be removably attached to the lever adjacent the outerends thereof.

A driving member in the form of a sprocket wheel 20 is rotatably mountedon the driven member I! and rotatably engages a bearing sleeve 22 whichembraces a portion of the driven member 12. The sprocket wheel may beconnected to a chain (not shown) which in turn may be connected througha variable speed mechanism, such as a Reeves drive, to a driving motor.A suitable lubricating attachment is preferably provided so that theparts may be properly lubricated and free rotation may exist between thesprocket wheel 20 and the member l2. A collar 26 is fixed to the end ofthe member I2 and engages the sprocket wheel 20 so as to affordconvenient assembly and prevent axial move.- ment in one direction ofthe sprocket wheel relative to the member I2 when the parts areassembled.

A resilient driving connection for driving in either direction ofrotation is provided between the sprocket wheel 20 and the driven memberI2, which includes a pair of disc members 28 and 30. The disc membersare rotatably mounted on the member I2 and bear against an annularshoulder 3I so that axial movement of the discs and the sprocket wheelin this direction is prevented. The disc 28 has an elongated curved slot32 therethrough; and the disc 30 has a similar slot 34 therethrough. Theslots 32 and 34 are described about the centers of the discs, one of theslots extending around one side of its disc andthe other slot extendingaround the opposite side of its disc. The driving connection between thewheel 28 and the respective disc is effected by a drive pin 36 which isfixed to the wheel 20 and which extends through both of the slots 32 and34. The arrangement of the pin 36 relative to the elongated slots 32 and34 thus afiords a lost motion connection between the wheel 26 and therespective disc so that as the wheel 20 is rotated in one direction, itengages one end of one of the slots causing a positive drive on thatparticular disc; and when rotated in the opposite direction, the pinengages the opposite end of the other slot effecting a positive drive ofthat particular disc in a manner that will become more apparentfrom thehereinafter detailed description of other parts of the mechanism.

The disc 28 has diametrically opposed radially extending ears 38 and 40formed integral therewith and the disc 38 has diametrically opposedradially extending similar ears 42 and 44 formed integral therewith. Theears 38, 40, 42, and 44 are arranged on their respective discs so thatwhen the discs are positioned relative to each other when. the mechanismis unloaded, the ears 38 and 44 are substantially 60 degrees apart andthe ears 40 and 42 are substantially 60 degrees apart. Axially extendingbosses 46, 48, 50, and 52 are provided on the ears 38, 40, 42, and 52,respectively, and extend axially toward the bosses I1 and I8 insubstantially the same cross-sectional plane.

To provide resilient driving connections between the respective discs 28and 38 and the driven membr I2 through the lever arms I6 and I8,elongated spiral spr; members are provided. When the mechanism isunloaded, the boss I! is adapted to lie intermediate the bosses 46 and58; and the boss I8 is. adaptedto lie intermediate the bosses 48 and. Aspiral spring 54 has one end connected to the boss I! and has itsopposite end connected to the boss 46; and a similar spring 56 has oneend connected to the ient connection between the driven member I2 andthe disc member 38, the spiral spring 58 has one end connected to theboss I1 and its opposite end connected to the boss 58; and a similarspring 88 has one end connected to the boss I9 andits opposite endconnected to the boss 52. to fix the spring members on the bosses I1 andI9, washers 62 may be slipped over the end of the In order 1 bosses andheld in place by suitable means, such as cotter pins; and the oppositeends of the springs may be attached to their respective bosses on thedisc members by similar means.

In the operation of the structure so far described, upon rotation of thesprocket wheel 26 in a counterclockwise direction, viewing Figs. 2; 4,and 6, the driving pin 38 engages the left hand end of the slot-32 andpositively drives the disc 28 in a counterclockwise direction. Thesprings 54 and 56 are loaded in tension and thus drive the member I2through the lever arms I6 and I8 in, a counterclockwise direction. Asthe load increases, the relative movement between the disc member 32 andthe lever arms I6 and I8 on the driven member I2 correspondinglyincreases with the result that the relative movement betweenthe sprocketwheel 20 and the member I2 correspondingly increases. -During rotationin this direction, the springs 58 and IiIlv are relaxed and no load isplaced thereon as the disc'30 is free to move within its slot 34relative to the driving pin 36.

With rotation of the sprocket wheel 20 in the opposite direction, thatis, clockwise, viewing Figs. 2', '4, and 6, the disc 30 is positivelydriven and the springs 58 and 88 are elongated as the load increases,with the springs 54 and 56 re- ,maining idle, the reverse action takingplace from that described above for a counterclockwise movement of thesprocket wheel 20.

From the above'description, it is evident that the relative movementbetween the sprocket wheel and the driven member increases as the loadincreases, and according to 'the present invention, such relativemovement is utilized to actuate mechanism, to be described, which inturn cuts out the driving motor when certain predetermined loads areexceeded. This mechanism includes a ring member III which is mounted foraxial movement relative to the driven member I2 and for rotationtherewith. A short tubular member I2, which is preferably aluminum orsimilar light weight material, is attached to the inner face of thedriven member I2 co-axial therewith in embracing relation to a boss I4on the inner face of the member I2. A suitable number, of screw membersI6 engagethe member 12 through the arm portions I6 and to attach themember I2 to the member I2. It is to be understood that the member I2could be formed integral with the member I2, in which event it would bepreferable to form the unitary structure of a strong, light-weightmaterial.

The ring member III has a hub portion I8 which slidably embraces the.peripheral surface of the tubular member I2 so that it may axially slidethereover. The ring I0 rotates with the driven member I2, and suchrotation is effected through a longitudinally extending guideway formedin the tubular member 12. A pair of roller members 82. are fixed to thehub portion I8 by means of screws 84, or the like, and extend within theguideway 80 engaging the side walls thereof as the ring member I8 ismoved axially of the tubular member I2. By-the 'use of the rollers82, aminimum of wear occurs between the parts I2 and the rollers so that therecording ring I0 is positively and firmly held against rotationrelative to. the member I2 with a minimum danger of looseness due towear. I

In order to cause the axial movement of th ring upon the application ofvarious loads to the control mechanisms, a cam ring 86 having a camfixed to that cup-shaped portion of the ring I surface 88 of requiredconfiguration is fixedly attached to the inner face of the sprocketwheel 20 'co-axial therewith. Suitable means such as screws 88 may beutilized for attaching the cam ring 88 to the wheel 20. While the camsurface 80 may be given various designs within the present invention,Fig. diagrammatically illustrates the'developed cam ring 86- accordingto the structural embodiment illustrated in Figs. 1 to 4, and 6.Inwardly extending rollers 90 are which extends toward the cam ring 88;and the rollers 90 are adapted to follow the cam surface 88 to effectthe axial movement of the recording ring I8.

In order to urge the ring toward the cam ring 86 so that the rollers atall times engage the cam surface 88, a spiral spring 92 is disposedwithin the tubular member 12. A transversely extending rod member94extends through longitudinally extending, diametrically opposed openings86 through the walls of the tubular member I2 and is fixed to therecording ring I8. The spring 02 is held within the tubular member 12and bears against the pin 94 by an end cap 08, suitably removablyattached to the exposed face-of the tubular member 12 by means of screws89, or the like. One end of the spring 92 engages over a co-axial hubportion IN on the capmember 88 and the other end bears against the pin84 so that the pin 94 and, therefore, the recording ring 10 are urgedtoward the cam ring 86. While in this embodiment the spring means 92 forurging the recording ring toward the cam ring, is illustrated as beingwithin the tubular member I2, it is evident that such a spring meanscould be placed on the outside of the tubular member I2 and bear.against the end of the hub portion I8 to accomplish the same result. Inthat event, it would merely be necessary to extend the peripheral edgeof the member 98 radially outwardly so as to engage the spring Theextent of axial movement of the ring 10 7 relative to the member I2 maybe used as an indicator of the torque by providing a scale I5 around themember 12. The position of the rear edge of the hub portion I8 on thescale thus indicates the applied torque.

As described above, as the load increases, relative movement between thedriving and driven member occurs. As the load increases from no load toover-load, the ring is caused to move axially away from the sprocketwheel 20. The line I03 in Fig. 1 illustrates the position of the ring atno-load; and when the mechanism is first started, the starting torquemoves the ring in the position indicated by the line I04; and at normalworking load, the ring settles to a position substantially indicated atline I05. When the ring reaches a predetermined point for apredetermined maximumload, movement beyond this point actuates a switchmechanism generally indicated at I06 which is connected in the circuitfor the driving motor and which operates to disconnectthe driving motorso as to prevent injury to the mechanism with which the device isoperatively associated. The switch I06 includes a lever arm I08 which ispivoted at IIO to a bracket I I2. The bracket I I2 may be mounted on asuitable base adjacent the recording ring I0 and to the rear thereof.The lever arm is normally urged toward the ring I0 by means of a leafspring II4.

Asupporting head H6 is threadably received within the top of the leverI08 facing the rear face of the ring. The head I I8 is adapted torotatably receive therein a. hardened ball member II8 which is spacedfrom the major portion of the inner walls of the head II8 by means ofsmall bearings I20. The ball H8 is thus free to rotate in all directionswithin the head II6. In order to adjust the position of the ball memberII8 with a relative degree of fineness, the

lever arm I08 is provided with a rearwardly directed shelf I22; and aset screw I24 is threadably received within a suitable opening in thebase H2 and is adapted to bear against the top of the shelf 22, Bythreadably adjusting the position of the screw I24, it is evident thatthe lever I08 may be set about the pivot IIO thus' to bear against theball member II8 when the mechanism is over-loaded. The normal positionof the ball member H8 is very slightly beyond the line I04, that whenthis load is exceeded the surface I32 engages the ball member II8tilting the lever I08 and tilting the mercury switch I26 to cut out themotor.

One important feature of the present invention is that the constructionand arrangement of the parts are such that the over-load controlmechanism becomes more sensitive to increases in load as the loadapproaches its maximum. For a better understanding of this, referencemay be had to Fig. 6 in which the reaction in one of the spring membersfor various positions is diagrammatically illustrated. It will beevident that the behaviour of the other spring members is'similar. Thenumerals A, B, C, and D illustrate the various positions for the boss 48as the load is increased. In order to illustrate the relative movement,the boss I8 is illustrated as remaining stationary while the boss 48 ismoved relative thereto. The spring 56 extends in a straight line betweenthe bosses 48 and I8 for all relative positions of the bosses. The lineI40 illustrates the position of the center line of the spring 58 forposition A; line I4I, for position B; line I42, for position C; and lineI43, for position D. The lever arm, against which the spring acts, isrepresented by a line from the center E perpendicular to the center lineof the spring 58 for its various positions. Thus line I50 represents thelever arm against which the spring acts fon position A; line I5Irepresents the lever arm for position B; line I52 represents the leverarm for position C; and line I53 represents the lever arm for positionD. Referring to Fig. 6, it is evident that as the load increases, thatis as the boss 48 moves toward position D, the lever arm against whichthe I28 of conventional con-' spring acts progressively decreases sothat this this could be reversed and the sprocket wheel 20 could be thedriven member and the member I2 be the driving member.

In Figs. 8 and 9, an embodiment of the present invention is illustratedin which the structure is adapted for use with a flexible coupling. Ashaft I10 may be considered as'the driving shaft and shaft I12 may beconsidered as the driven shaft. A plate member I14 is keyed to one endof the shaft I10 for rotation therewith and has a hub portion I16 whichembraces the inner end of the shaft I10. The discs 28 and 30 arerotatably mounted on the inner portion of the hub I18 and. are fixed inplace by means of a collar I80 which may be fixed to the hub I16. Thedriving pin 36 is fixed to and extends through the member I14 andengages the disc members 28 and 30 through their respective slots 32 and34 as in the embodiment described above. The cam ring 86 is formedintegral with the member I14, or it may be formed separately andsuitably attached thereto, and the cam face 88 of the cam ring 86 isadapted to engage the rollers 80 of the recording ring 10 in the samemanner as in the embodiment described above.

The driven shaft I12 has the hub I80 of a lever member I82 keyed theretofor rotation with the shaft I12. The lever member I82 corresponds to themember I2 in the embodiment described above, and has the radiallyextending arms IE and I8 which have the bosses I1 and I9, respectively,on the outer ends thereof. The springs 54, 56, 58 and 80 are provided inthe embodiment illustrated in Fig. 8 in the same relationship as in theembodiment described above, so that the driving connection between themembers I14 and I18 in Fig. 8 is substantially the same as the drivingconnection between the sprocket 20 and the driven member I2 in theembodiment described in connection with Figs. 1 to '7. (Member I82 hasdiametrically opposed radially extending elongated grooves I90 thereinwhich correspond to the grooves 80 and which are adapted to slidablyreceive therein the rollers 82.)

In this embodiment two pairs of rollers diametrically opposed areprovided and attached to the recording ring 10. L-shaped bracket membersI92 are fixed to the inner ends of screws 84 and have fixed thereto anannular member I84 which surrounds the hub I80 and against which thespring 82 bears in order to urge the recording ring 10 against the camring 86. In this embodiment the spring 82 embraces the hub portion I80and is held in place by means of an end cap I08 fixed to the hub portion80 for rotation therewith.

The longitudinal guideways for the rollers 82 which permit the axialmovement of the recording valve 10 are formed by split rings I88 and I99providing spaces therebetween to form the longitudinally extendinggroove 20I therebetween. The rings I88 and I88.are fixed to the memberI82 for rotation therewith so that the recording valve 10 rotates withthe member I82.

The operation of the structure illustrated in Figs. 8 and 9 issubstantially the same as that in the embodiment illustrated in Figs. 1to '7, and it is not believed that it is necessary to discuss in detailthe operation of this embodiment. It is suificient to say that uponapplication of over load the recording valve 10 moves into engagementwith the ball member H8 and actuates the switch I08 to disconnect thedriving mechanism. While both embodiments have been illustrated inassociation with a mercury switch, it is eviiql-s n, l uv dent thatother forms of cut-outs may be employed, such as a limit switch.

Formal changes may be made in the specific embodiments of the inventiondescribed without departing from the spirit and substance of theinvention, the scope of which is commensurate with the appended claims.

What is claimed is:

1. The combination of a drive element, a driven element, and torquecontrolled means providing a driving connection between said elements,said last named means including a member fixedly connected to one ofsaid elements, disc members connected to the other of said elements forrotation therewith, spring means connecting said first named member andsaid disc members respectively providing a resilient connectiontherebetween, the construction and arrangement of said spring meansrelative to said disc members and to said first named members being suchthat the lever arm against which the spring acts decreases with increasein load.

2. The combination of a drive element, a driven element, and torquecontrolled means providing a driving connection between said element,said last named means including a member fixedly connected to one ofsaid. elements, disc members connected to the other of said elements forrotation therewith, spring means unconfined throughout their lengthconnecting said first named member and said disc members respectivelyproviding a resilient connection therebetween, the construction andarrangement of said spring means relative to said disc members and tosaid first named members being such that the lever arm against which thespring acts decreases with increase in load.

3. The combination of a drive element, a driven element, and torquecontrolled means providing a driving connection between said elements,said last named means including a member fixedly connected to one ofsaid elements, disc members connected to the other of said elements forrotation therewith, spiral springs connecting said first named member,and said disc members respectively providing a resilient connectiontherebetween, said spiral springs lying in straight lines at all times,the construction and arrangement of said spiral springs relative to saiddisc members and to said first named member being such that the leverarm against which the springs act decreases with increase in load.

4. The combination of a. driving element, a driven element, and meansproviding a driving connection between said elements, said last namedmeans including a member fixedly connected to one of said elements, apair of disc members, meansmounting said disc members to the other ofsaid elements for rotation therewith, resilient means connecting saidfirst named member and said disc members respectively, the connectionbetween said disc members and said other of said elements being soconstructed that said disc members may rotate relative to each other soas to provide a lost motion connection between said disc members andsaid other of said elements.

5. The combination of a, driving element, a

driven element, and torque controlled means providing a drivingconnection between said ele- 'ments, said last named means including amember fixedly connected to one of said elements, disc members havingelongated operangs therethrough, a pin member extending through saidelongated openings and fixed to the other of said elements to provide alost motion connection between said disc members and said other of saidelements, spring means connecting said first named member and said discmembers respectively providing a resilient connection therebetween, theconstruction and arrangement of said spring means relative to said discmembers and to said first named member being such that the lever armagainst which the spring acts decreases with increase in load.

6. The combination of a driving element, a driven element, and torquecontrolled means pro viding a driving connection between said elements,saidlast named means including a member fixedly connected to one of saidelements, disc members connected to the other of said elements forrotation therewith, spring means connecting said first named member andsaid disc members respectively providing a resilient connectiontherebetween and permitting relative movement therebetween, an annularmember connected to one of said elements and extending radiallyoutwardly therebeyond, means connecting said annular member with saidone of said elements for I axial movement relative thereto, saidconnecting means including a roller secured to said annular memberadjacent the inner edge thereof which engages in an elongated slot insaid one of said elements so that said annular member is rotated withsaid one of said elements and is movable 3 axially relative thereto, acam ring fixed to the other 01' said elements, and a roller mounted onsaid annular member radially outwardly disposed from said first namedroller element adapted to be engaged by said cam ring to cause saidaxial movement. 7

'7. The combination of a driving element, a

driven element, and torque controlled means providing a drivingconnection between said elements, said last named means including afirst member fixedly connected to one of said elements, a second memberconnected to the other of said elements for rotation therewith,resilient means connecting said first and second named members, anannular member connected to one of said elements and extending radiallyoutwardly therebeyond, means connecting said annular member with saidone of said elements for axial movement relative thereto, saidconnecting means including a roller element secured to said annularmember and located toward the center thereof which engages in anelongated slot in said one of said elements so that said annular memberis rotated with said one of said elements and is movable axiallyrelative thereto, a cam ring fixed to the other of said. elements, and aroller mounted on said annular member disposed outwardly from said firstnamed roller adapted to be engaged by said cam ring to cause said axialmovement.

ERIC 0. mm.

